1. Field of the Invention
The present invention relates to a lithographic apparatus and a device manufacturing method.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices involving fine structures. In a conventional lithographic apparatus, a patterning means, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC (or other device, such as a flat panel display), and this pattern can be imaged onto a target portion (e.g., comprising part of, one or several dies) on a substrate (e.g., a silicon wafer or glass plate) that has a layer of radiation-sensitive material (resist). Instead of a mask, the patterning means may comprise an array of individually controllable elements which serve to generate the circuit pattern.
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one pass, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
In a lithographic projection apparatus using arrays of individually controllable elements, it is often necessary to use a plurality of such arrays in order to expose the pattern on a substrate sufficiently quickly that the though-put time for a substrate being exposed in the apparatus is economical. Furthermore, each array requires a relatively large amount of space around it for its support services such as data or control lines required for setting the pattern on each array. It is therefore not appropriate to simply illuminate all of the arrays simultaneously with a single illumination field.
What is needed, therefore, is an approach to provide an arrangement for supplying radiation to each of the arrays of individually controllable elements that is economical and does not introduce additional sources of production error in the pattern exposed on the substrate.